Successful Use of Intrathecal Carboxypeptidase G2 for Intrathecal Methotrexate Overdose: A Case Study and Review of the Literature

Navigating methotrexate toxicity: Examining the therapeutic roles of folinic acid and glucarpidase

Methotrexate (MTX) toxicity varies depending on factors such as dosing frequency (acute or repeated), dosage (low or high) and the administration route (oral, parenteral or intrathecal). Renal impairment can trigger or exacerbate MTX toxicity. Acute oral low-dose MTX (LDMTX) overdoses seldom lead to toxicity due to the saturable maximal bioavailable dose, but toxicity risks increase with repeated low doses (>3 days), high-dose MTX (HDMTX) or intrathecal poisoning. Folinic acid shares MTX transporters in the gut and cells and bypasses the MTX-induced dihydrofolate reductase inhibition. The required folinic acid dosage differs for low-dose and high-dose MTX toxicities. Acute LDMTX poisoning rarely requires folinic acid, while chronic LDMTX poisoning needs low-dose folinic acid until cellular function is restored. In HDMTX toxicities, early intravenous folinic acid administration is recommended, with dose and duration being guided by MTX concentrations and clinical improvement. In intrathecal MTX poisoning, folinic acid should be administered intravenously. Glucarpidase, a recombinant bacterial enzyme, has a high affinity for MTX and folate analogues in the intravascular or intrathecal systems. It decreases serum MTX concentrations by 90%-95% within 15 min. Its primary indication is for intrathecal MTX poisoning. It is rarely indicated in HDMTX toxicity unless patients have renal injury. However, there is no literature evidence supporting its use in HDMTX poisoning. Its use is limited by its significant cost and lack of availability. Haemodialysis can be potentially useful for MTX removal in cases where glucarpidase is not available. Additionally, fluid hydration, renal support and urine alkalinization are important adjunctive therapies for managing MTX toxicities.

Molecular bowls for inclusion complexation of toxic anticancer drug methotrexate

We describe the preparation and study of novel cavitands, molecular bowls 16+ and 26+, as good binders of the anticancer drug methotrexate (MTX). Molecular bowls are comprised of a curved tribenzotriquinacene (TBTQ) core conjugated to three macrocyclic pyridinium units at the top. The cavitands are easily accessible via two synthetic steps from hexabromo-tribenzotriquinacene in 25% yield. As amphiphilic molecules, bowls 16+ and 26+ self-associate in water by the nucleation-to-aggregation pathway (NMR). The bowls are preorganized, having a semi-rigid framework comprising a fixed bottom with a wobbling pyridinium rim (VT NMR and MD). Further studies, both experimental (NMR) and computational (DFT and MCMM), suggested that a folded MTX occupies the cavity of bowls wherein it forms π-π, C-H-π, and ion pairing intermolecular contacts but also undergoes desolvation to give stable binary complexes (μM) in water. Moreover, a computational protocol is introduced to identify docking pose(s) of MTX inside molecular bowls from NMR shielding data. Both molecular bowls have shown in vitro biocompatibility with liver and kidney cell lines (MTS assay). As bowl 26+ is the strongest binder of MTX reported to date, we envision it as an excellent candidate for further studies on the way toward developing an antidote capable of removing MTX from overdosed cancer patients.

The leptomeninges as a critical organ for normal CNS development and function: First patient and public involved systematic review of arachnoiditis (chronic meningitis)

BACKGROUND & IMPORTANCE

This patient and public-involved systematic review originally focused on arachnoiditis, a supposedly rare "iatrogenic chronic meningitis" causing permanent neurologic damage and intractable pain. We sought to prove disease existence, causation, symptoms, and inform future directions. After 63 terms for the same pathology were found, the study was renamed Diseases of the Leptomeninges (DLMs). We present results that nullify traditional clinical thinking about DLMs, answer study questions, and create a unified path forward.

METHODS

The prospective PRISMA protocol is published at Arcsology.org. We used four platforms, 10 sources, extraction software, and critical review with ≥2 researchers at each phase. All human sources to 12/6/2020 were eligible for qualitative synthesis utilizing R. Weekly updates since cutoff strengthen conclusions.

RESULTS

Included were 887/14286 sources containing 12721 DLMs patients. Pathology involves the subarachnoid space (SAS) and pia. DLMs occurred in all countries as a contributor to the top 10 causes of disability-adjusted life years lost, with communicable diseases (CDs) predominating. In the USA, the ratio of CDs to iatrogenic causes is 2.4:1, contradicting arachnoiditis literature. Spinal fusion surgery comprised 54.7% of the iatrogenic category, with rhBMP-2 resulting in 2.4x more DLMs than no use (p<0.0001). Spinal injections and neuraxial anesthesia procedures cause 1.1%, and 0.2% permanent DLMs, respectively. Syringomyelia, hydrocephalus, and arachnoid cysts are complications caused by blocked CSF flow. CNS neuron death occurs due to insufficient arterial supply from compromised vasculature and nerves traversing the SAS. Contrast MRI is currently the diagnostic test of choice. Lack of radiologist recognition is problematic.

DISCUSSION & CONCLUSION

DLMs are common. The LM clinically functions as an organ with critical CNS-sustaining roles involving the SAS-pia structure, enclosed cells, lymphatics, and biologic pathways. Cases involve all specialties. Causes are numerous, symptoms predictable, and outcomes dependent on time to treatment and extent of residual SAS damage. An international disease classification and possible treatment trials are proposed.

Half-dose glucarpidase as efficient rescue for toxic methotrexate levels in patients with acute kidney injury

Purpose

High-dose methotrexate (HDMTX)-associated acute kidney injury with delayed MTX clearance has been linked to an excess in MTX-induced toxicities. Glucarpidase is a recombinant enzyme that rapidly hydrolyzes MTX into non-toxic metabolites. The recommended dose of glucarpidase is 50 U/kg, which has never been formally established in a dose finding study in humans. Few case reports, mostly in children, suggest that lower doses of glucarpidase might be equally effective in lowering MTX levels.

Methods

Seven patients with toxic MTX plasma concentrations following HDMTX therapy were treated with half-dose glucarpidase (mean 25 U/kg, range 17–32 U/kg). MTX levels were measured immunologically as well as by liquid chromatography–mass spectrometry (LC–MS). Toxicities were assessed according to National Cancer Institute—Common Terminology Criteria for Adverse Events (CTCAE) v5.0.

Results

All patients experienced HDMTX-associated kidney injury (median increase in creatinine levels within 48 h after HDMTX initiation compared to baseline of 251%, range 80–455%) and showed toxic MTX plasma concentrations (range 3.1–182.4 µmol/L) before glucarpidase injection. The drug was administered 42–70 h after HDMTX initiation. Within one day after glucarpidase injection, MTX plasma concentrations decreased by ≥ 97.7% translating into levels of 0.02–2.03 µmol/L. MTX rebound was detected in plasma 42–73 h after glucarpidase initiation, but concentrations remained consistent at < 10 µmol/L.

Conclusion

Half-dose glucarpidase seems to be effective in lowering MTX levels to concentrations manageable with continued intensified folinic acid rescue.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00280-021-04361-8.

Treatment of two cases on the same day of intrathecal methotrexate overdose using cerebrospinal fluid exchange and intrathecal instillation of carboxypeptidase-G2

BACKGROUND

Two 14-year old boys with acute lymphocytic leukemia were treated according to the NOPHO-ALL-08 protocol with intrathecal methotrexate (MTX) on the same day. Due to a preparation error in the hospital pharmacy, they were both given 240 mg of MTX instead of the prescribed 12 mg. Treatment (or methods): Both patients developed acute neurotoxicity with confusion, pain and seizures. Intravenous dexamethasone and folinic acid (leucovorin) was given. Exchange of cerebrospinal fluid was performed. Intrathecal glucarpidase (carboxypeptidase-G2) was administered after 11 h.

RESULTS

One patient developed a toxic arachnoiditis. Three years after the incident, one patient has no neurological or neuropsychological sequelae after the overdose, while the other reports some loss of short-term memory.

CONCLUSION

Fast recognition and treatment of intrathecal MTX overdose is critical to survival and outcome. Efforts to prevent such overdoses are of vital importance.

Intrathecal chemotherapy: potential for medication error

BACKGROUND

The central nervous system is a unique sanctuary site for malignant disease. To ensure optimal disease control, intrathecal (IT) chemotherapy is commonly given in conjunction with standard chemotherapy protocols, thus providing the opportunity for medication errors.

OBJECTIVE

A systematic review of the current literature on medication errors associated with the administration of IT chemotherapy was conducted.

METHODS

English-language literature published from January 1960 through June 2013 was accessed. Case reports, clinical studies, and review articles pertaining to IT medication errors were included in the review. References of all relevant articles were searched for additional citations.

RESULTS

Twenty-two cases of accidental IT overdoses have been reported with methotrexate and 1 with cytarabine. There have been numerous cases of antineoplastic agents intended for administration by the parenteral route being inadvertently given intrathecally. Vincristine has been implicated 31 times (25 deaths), as well as vindesine, asparaginase, bortezomib, daunorubicin, and dactinomycin. This has led to profound toxicity and, commonly, death. Unfortunately, many cases go unrecognized or unreported.

CONCLUSIONS

The best method for eliminating the risk of IT medication errors is to develop effective methods of prevention and incorporate them into oncology and hematology practice internationally. Strategies include abolishing the syringe as a method of vinca alkaloid administration and substituting small-volume intravenous bags, and developing novel methods for intraspinal drug administration.

IMPLICATIONS FOR PRACTICE

The nursing profession is in a unique position to influence change and lead the way in establishing preventative strategies into current practice.

Antidotes to coumarins, isoniazid, methotrexate and thyroxine, toxins that work via metabolic processes

Some toxins cause their effects by affecting physiological processes that are fundamental to cell function or cause systemic effects as a result of cellular interaction. This review focuses on four examples, coumarin anticoagulants, isoniazid, methotrexate and thyroxine from the context of management of overdose as seen in acute general hospitals. The current basic clinical pharmacology of the toxin, the clinical features in overdose and evidence base for specific antidotes are discussed. The treatment for this group is based on an understanding of the toxic mechanism, but studies to determine the optimum dose of antidote are still required in all these toxins except thyroxine, where treatment dose is based on symptoms resulting from the overdose.

Development of a policy and procedure for accidental chemotherapy overdose

A policy regarding rapid response to chemotherapy overdoses was developed by the authors in an attempt to minimize morbidity and mortality. The parameters of a chemotherapy overdose were defined to promote early recognition of an overdose incident. Resources needed to guide potential therapeutic interventions and required monitoring were developed. The policy defines the immediate actions to be taken in the event of a chemotherapy overdose. The availability of a chemotherapy overdose policy provides an enhanced level of safety for patients by ensuring that appropriate treatment is initiated without delay. The development of the policy was in response to the reporting of a tragic error at another institution. Healthcare providers must recognize and address potential areas of vulnerability to maximize patient safety.